High-Precision Measurements of Activation Energies over Small Temperature Intervals: Curvature in the Arrhenius Plot for the Reaction NO + O3 -> NO2 + O2

Article abstract of DOI:10.1021/j100214a007

Activation energies for the reaction between nitric oxide and ozone were measured over temperature intervals as small as 10 K with a typical precision of 3percent, by using a new dual flow tube technique with chemiluminescence detection.The local activation energy was found to increase by 660 +/-90 cal between 200 and 350 K.The activation energy is given by E_a=1520 +/-230 + (2.2 +/-0.3)RT cal, and the best expression for predicting the absolute rate constant is k₁=8.9E-19T^2.2e^-1520/RT cm³molecule^-1s^-1, which predicts k₁(298 K)=1.90E-14, in good agreement with previous results.This expression for K₁ is expected to be accurate to +/-10percent in the temperature range 200-350 K.Contributions to curvature in the Arrhenius plot due to the temperature dependence of the preexponential factor, the two product channels for the reaction, and reaction rate enhancement by vibrationally excited ozone are discussed.